Japanese Beetles Are on My Rose Bushes

Why Roses

• Japanese beetles are attracted by the bright foliage and sweet scent of roses, and they stay for the delicious meals they find. In general, the beetles feed only on soft parts of a flower, so a tell-tale sign of a beetle infestation is leaves with the veins intact but the soft parts chewed out. However, the entirety of a rose petal is soft and delicate, making these plants an easy meal. They will also devour the leaves of the bush.

Effects on Roses

• The beetles can devastate a rose bush in the matter of only a day or two. Once a beetle finds a happy place to live and eat, he puts off pheromones that attract others to the same area, so the infestation can multiply in a matter of hours. The bugs will devour rose petals, leading to a chewed up appearance and significant defoliation, or petals falling off of the bush. You will also notice the leaves looking chewed through or falling off. The entire plant will eventually begin to turn brown and wilt, and may eventually die off completely.

Chemical Control

• Insecticidal soaps will not harm the rose bush itself, and will kill any beetles with which they come in contact. However, this treatment will not stay on the bush, and so will not prevent more beetles from arriving. Some insecticides are designed specifically to combat Japanese beetles, so be sure to read the label thoroughly before choosing a product. However, some of these poisons actually attract more bugs to the source so that they can kill more insects, but until they die, those insects will do extensive damage to your rose bush. Consider treating only a single bush and hoping that all of the bugs crowd there and away from your other bushes.

Cultural Control

• Japanese beetles have no natural predators, since their shells are so hard, so encouraging birds or predatory insects will have little to no effect on the beetle population. Instead, cover sensitive rose bushes with fine mesh netting like cheesecloth, which will allow water, air and sunlight to flow through but will keep the bugs off of the foliage itself. Because the beetles are easy to see, you can individually remove beetles from the rose bush and dispose of them in soapy water or an insecticide. Milky spore is a natural bacteria that kills young Japanese beetles, essentially preventing them from reproducing, but is extremely expensive and doesn't prevent new beetles from moving in. You can also consider planting strong herbs like garlic nearby to drive the beetles away with foul smells and mask the sweet smell of roses.